Finding the length of a pipe (segment) over terrain

I would like to approximate the physical length of a pipe that is traversing the surface of a sloped face. Calculating the length using the tool "calculate geometry attributes" provides two very different options.

Calculating length (geodesic) equates to 163 ft And calculating length (3D) equates to 193 ft

Which option is more accurate to resolve my situation?

I've tried using google earth as well...regardless, the ruler options they provide are confusing.